WASHINGTON (CNN) -- Texas state officials went to federal court Monday to defend a controversial new voter identification law, dismissing suggestions the requirement would deny hundreds of thousands of people -- many of them minorities -- access to the ballot.

A weeklong trial kicked off in Washington before a special panel of three federal judges who will decide whether the law, known as SB 14, should be allowed to go into effect. It is one of several legal challenges to voter ID laws around the country.

A key enforcement provision of the landmark Voting Rights Act of 1965 -- known as Section 5 -- gives the federal government open-ended oversight of states and localities with a history of voter discrimination. Any changes in voting laws and procedures in the covered areas must be "pre-cleared" with Washington. That provision was reauthorized in 2006 for another quarter-century.

The Justice Department in March rejected the Texas law, passed in 2011, using the state's own statistics to show about 600,000 registered voters there lack a state-issued driver's license or identification card. SB 14 amended an earlier voter identification law.

Texas is among eight states to require official photo identification in an effort to stop what officials say is voter fraud. Opponents of the laws say they disenfranchise poor, minority and disabled voters. Obama administration officials have concluded there is little evidence of voter fraud in Texas warranting the legislative changes.

"We note that the state's submission did not include evidence of significant in-person voter impersonation not already addressed by the state's existing laws," Thomas Perez, assistant attorney general, said in March.

A key supporter of the law told the judicial panel Monday that having valid, government-issued photo identification is a reasonable, modern-day necessity.

"The public expected us to pass legislation to give them confidence in the system," said Jose Luis Aliseda, a Texas state legislator. The Republican from rural south Texas said he has been privately approached by a number of constituents -- many older Hispanic citizens -- claiming they were pressured to cast fraudulent ballots. That brought objections from lawyers representing groups opposing the law, and mild skepticism from the judges.

Keith Ingram, the director of Texas' elections division, also testified the law is justified. He cited tiny Loving County in the isolated western part of the state with a population only around 70 people, but voter registration of 157% of that number.

Statewide, Ingram said his office had identified at least 239 dead people casting a ballot in the past year. But he conceded under cross-examination some of that total may have resulted from clerical error, and that only four people "definitely" were part of voter fraud.

"The U.S. Supreme Court has already ruled that voter identification laws are constitutional," said Texas Attorney General Greg Abbott. "Texas should be allowed the same authority other states have to protect the integrity of elections."

Election fraud investigations by the Texas attorney general's office in the past decade have resulted in 50 convictions, Abbott said.

But a coalition of minority and civil rights groups has said the Texas law is among the most restrictive in the nation. Among those bringing suit are students from historically black universities Prairie View A&M and Southern. They argue the new law would mean student ID cards would no longer be recognized for voting purposes.

Nationwide, the NAACP claims 25% of African-Americans and 16% of Latinos of voting age lack a current government-issued photo ID.

"Texas's discriminatory photo ID measure demonstrates why, in the face of persisting obstacles for minority voters, the Voting Rights Act is still necessary," said Natasha Korgaonkar, an attorney with the civil rights group's Legal Defense Fund. "Our clients expose the discriminatory nature of Texas's photo ID measure, and the true costs and burdens of obtaining the underlying documents necessary to secure Texas's so-called 'free' photo ID. Our experience teaches us that a student's ability to pay a fee should not determine whether they can vote."

The Justice Department had concluded that while the state provides free ID cards for those seeking them to vote, they would have to be obtained in person, a burden for many residents, especially in isolated regions. The federal government said 81 of the state's 254 counties do not have offices where people can get the cards.

Among those set to testify Tuesday is Democratic state lawmaker Trey Martinez Fischer, who is also chairman of the Mexican American Legislative Caucus. He argues Texas voting procedures need to remain under federal monitoring.

"This is about ensuring that every American is respected, that our voices are heard, and that the promise of America continues to thrive," said Martinez Fischer. "Photo identification laws could take us back to the era of the poll tax. They could have a chilling effect at the polls, and we have never solved anything in America with less democracy."

A similar voter ID law in South Carolina was blocked by the Obama administration in December. A federal court hearing in that case is set for late August.

Opponents of the voter ID law in Texas have said it could suppress minority voter turnout by 3% to 5% at a time when the Hispanic population there is growing rapidly. There have also been complaints the new law has not been sufficiently publicized.

The Justice Department said Hispanic registered voters in Texas are 46.5% to 120% more likely than a non-Hispanic registered voter to lack the required identification.

The nation's second largest state has a population of 25.1 million, an increase of 4.3 million in the past decade. That explosive growth ensures Texas will gain four congressional seats, requiring new voting boundaries.

The U.S. Supreme Court in January ruled on another aspect of Texas voting law, the new boundaries for state and congressional offices created by Republican state lawmakers. The justices unanimously tossed out a revised map created by a federal judicial panel, which had differed substantially from the one originally conceived by the legislature.

"To the extent the (federal) District Court exceeded its mission to draw interim maps that do not violate the Constitution or the Voting Rights Act, and substituted its own concept of 'the collective public good' for the Texas Legislature's determination of which policies serve 'the interests of the citizens of Texas,' the court erred," said the Supreme Court ruling.

The state held its primary election in late May, using maps largely like the ones drawn by the legislature.

The high court in 2008 allowed Indiana's voter ID law to stand, saying the stated goal of stopping voter fraud was a legitimate exercise of legislative power.

The federal judicial panel in the Texas ID dispute is not expected to rule from the bench, and a ruling could be weeks away.